There are many advantages to the use of light emitting diode (LED) die packages as light sources in light fixtures to produce light efficiently. Many light fixtures have incorporated one or more arrays of LED light modules, each of which includes one or more LED arrays, to emit the desired lumen output and shape of the light output. Some of these light fixtures are used in applications for street lighting, pathway lighting, parking structure lighting, decorative lighting, and any other type of spread beam applications.
Typically, the LED arrays are made up of LED die packages that each include an LED light source with a lens (or primary optic), where each of the LED die packages are in turn associated with an optical system (or secondary optic) to control and/or maximize the light emitted from the LED die package. In other configurations, the LED light source may only have one over-optic to refract light. Each of the secondary optics aligned with the LED light source may be varied in shape and/or individually rotated to create a beam pattern for the array that is unique from the devices themselves, including all degrees of freedom, e.g. separately determined translation, tilt, and yaw for each lens. The array may include similarly colored LEDs, white or otherwise, or various colored LEDs.
The LED die packages are typically coupled to a front surface of a printed circuit board which electrically couples the LED die packages to a power source. The printed circuit board may further include circuitry to drive the LED die packages, or LEDs, included in one or more arrays of LED light sources. In the lighting applications mentioned above, the light fixtures typically include a heat sink that is coupled directly to a rear surface of the printed circuit board. Typically, the printed circuit board is coupled to a surface of the heat sink by inserting screws, or other fastening devices, through one or more holes formed within the printed circuit board and into one or more corresponding openings formed within the heat sink. The heat sink is typically made of heat conductive aluminum alloy and may provide heat dissipation to allow proper cooling of the LEDs. Alternatively, the heat sink is fabricated using other thermally conductive materials.
These heat sinks are generally exposed to the surrounding environment and may allow water, from rain, to enter into the circuitry area of the printed circuit board from the heat sink and the rear surface of the printed circuit board. Specifically, water may enter through the holes formed within the printed circuit board and/or through the sides portions of the printed circuit board. If the water is acidic, the water entering into the circuitry area of the printed circuit board can cause the printed circuit board to fail, thereby causing expenses, in material and labor, to fix the light fixture and inconvenience to passersby for a time period when light is no longer emitted from the failed LED light module.